This invention relates to a system and process for the separation and refining of rare earths. In this system a dilute solution of rare earths resulting from the step of separating and refining the rare earths by using an ion exchanger is concentrated by a process for separation by a reverse osmosis membrane and is thereby reduced in volume, while the water which has passed through the membrane is circulated for reuse in the step of separating and refining the rare earths.
Although various processes are available for the separation and refining of rare earths, a process using an ion exchanger is generally employed for the separation and refining of rare earths to high purity.
The process in which an ion exchanger is used for the separation and refining of rare earths, however, has a number of drawbacks, as an eluate of rare earths is produced in a very large quantity. It requires a large number of large tanks, and centrifugal dehydrators, pumps, pipelines, valves, etc., each having a large capacity. It also requires a large amount of water. Thus, it requires expensive equipment. The precipitation and recovery of an eluant and the precipitation and separation of rare earths necessitate the use of large amounts of chemicals and water.
Other drawbacks of the process include the necessity of using large amounts of chemical diluting water, washing water and hot water for preparing the ion exchanger, and the necessity of using a large amount of water for cooling the eluate.